AEROPLANE CONSTRUCTION
As may be inferred from the foregoing statements,
there are no definite rules for the construction
of either type of flying machine, as the
flying models vary to such an extent that it is
difficult to take either of them as a model to represent
the preferred type of construction.
LATERAL, AND FORE AND AFT.--The term lateral
should be understood, as applied to aeroplanes.
It is always used to designate the direction at
right angles to the movement of the machine.
Fore and aft is a marine term meaning lengthwise,
or from front to rear, hence is always at right
angles to the lateral direction.
The term transverse is equivalent to lateral,
in flying machine parlance, but there is this
distinction: Transverse has reference to a machine
or object which, like the main planes of an aeroplane,
are broader, (that is,--from end to end)
than their length, (from front to rear).
On the other hand, lateral has reference to side
branches, as, for instance, the monoplane wings,
which branch out from the sides of the fore and
aft body.
STABILITY AND STABILIZATION.--These terms constantly
appear in describing machines and their
operations. If the flying structure, whatever it
may be, has means whereby it is kept from rocking
from side to side, it has stability, which is usually
designated as lateral stability. The mechanism
for doing this is called a stabilizer.
THE WRIGHT SYSTEM.--The Wright machine has
reference solely to the matter of laterally controlling
the flying structure, and does not pertain
to the form or shape of the planes.
In Fig. 49 A designates the upper and lower
planes of a Wright machine, with the peculiar
rounded ends. The ends of the planes are so
arranged that the rear margins may be raised or
lowered, independently of the other portions of
the planes, which are rigid. This movement is
indicated in sketch 1, where the movable part B
is, as we might say, hinged along the line C.
The dotted line D on the right hand end, shows
how the section is depressed, while the dotted
lines E at the left hand end shows the section
raised. It is obvious that the downturned ends,
as at D, will give a positive angle at one end of the
planes, and the upturned wings E at the other end
will give a negative angle, and thus cause the right
hand end to raise, and the other end to move
downwardly, as the machine moves forwardly
through the air.
CONTROLLING THE WARPING ENDS.--Originally
the Wrights controlled these warping sections by
means of a cradle occupied by the aviator, so that
the cradle would move or rock, dependent on the
tilt of the machine. This was what was termed
automatic control. This was found to be unsatisfactory,
and the control has now been placed so
that it connects with a lever and is operated by
the aviator, and is called Manually-operated control.
In all forms of control the wings on one side are
depressed on one side and correspondingly elevated
on the other.
THE CURTIS WINGS.--Curtis has small wings,
or ailerons, intermediate the supporting surfaces,
and at their extremities, as shown in sketch 2.
These are controlled by a shoulder rack or swinging
frame operated by the driver, so that the body
in swinging laterally will change the two wings
at the same time, but with angles in different
directions.
THE FARMAN AILERONS.--Farman's disposition
is somewhat different, as shown in sketch 3. The
wings are hinged to the upper planes at their rear
edges, and near the extremities of the planes.
Operating wires lead to a lever within reach of the
aviator, and, by this means, the wings are held at
any desired angle, or changed at will.
The difficulty of using any particular model, is
true, also, of the arrangement of the fore and aft
control, as well as the means for laterally stabilizing
it. In view of this we shall submit a general
form, which may be departed from at will.
FEATURES WELL DEVELOPED.--Certain features
are fairly well developed, however. One is the
angle of the supporting plane, with reference to
the frame itself; and the other is the height at
which the tail and rudder should be placed above
the surface of the ground when the machine is at
rest.
DEPRESSING THE REAR END.--This latter is a
matter which must be taken into consideration,
because in initiating flight the rear end of the
frame is depressed in order to give a sufficient
angle to the supporting planes so as to be able to
inaugurate flight.
In order to commence building we should have
some definite idea with respect to the power, as
this will, in a measure, determine the area of the
supporting surfaces, as a whole, and from this
the sizes of the different planes may be determined.
DETERMINING THE SIZE.--Suppose we decide on
300 square feet of sustaining surface. This may
require a 30, a 40 or a 50 horse power motor,
dependent on the speed required, and much higher
power has been used on that area.
However, let us assume that a forty horse power
motor is available, our 300 square feet of surface
may be put into two planes, each having 150 square
feet of surface, which would make each 5' by 30'
in size; or, it may be decided to make the planes
narrower, and proportionally longer. This is immaterial.
The shorter the planes transversely,
the greater will be the stability, and the wider the
planes the less will be the lift, comparatively.
RULE FOR PLACING THE PLANES.--The rule for
placing the planes is to place them apart a distance
equal to the width of the planes themselves,
so that if we decide on making them five feet wide,
they should be placed at least five feet apart.
This rule, while it is an admirable one for slow
movements or when starting flight, is not of any
advantage while in rapid flight.
If the machine is made with front and rear
horizontally-disposed rudders, or elevators, they
also serve as sustaining surfaces, which, for the
present will be disregarded.
Lay off a square A, Fig. 49a, in which the vertical
lines B, B, and the horizontal lines C, C, are
5' long, and draw a cross D within this, the lines
running diagonally from the corners.
Now step off from the center cross line D, three
spaces, each five feet long, to a point E, and join
this point by means of upper and lower bars F,
G, with the upper and lower planes, so as to form
the tail frame.
_Fig. 49a. Rule for spacing Planes._
As shown in Fig. 50, the planes should now be
indicated, and placed at an angle of about 8 degrees
angle, which are illustrated, H being the
upper and I the lower plane. Midway between the
forward edges of the two planes, is a horizontal
line J, extending forwardly, and by stepping off
the width of two planes, a point K is made, which
forms the apex of a frame L, the rear ends of the
bars being attached to the respective planes H, I,
at their forward edges.
_Fig. 50. Frame of Control Planes._
_Fig. 51. and Fig. 52._
ELEVATING PLANES.--We must now have the general
side elevation of the frame, the planes, their
angles, the tail and the rudder support, and the
frame for the forward elevator.
To this may be added the forward elevating
plane L, the rear elevator, or tail M, and the vertical
steering rudder N.
The frame which supports the structure thus
described, may be made in a variety of ways, the
object being to provide a resilient connection for
the rear wheel O.
Fig. 52 shows a frame which is simple in construction
and easily attached. The lower fore
and aft side bars P have the single front wheel
axle at the forward end, and the aft double wheels
at the rear end, a flexible bar Q, running from the
rear wheel axle to the forward end of the lower
plane.
A compression spring R is also mounted between
the bar and rear end of the lower plane to
take the shock of landing. The forward end of
the bar P has a brace S extending up to the front
edge of the lower plane, and another brace T connects
the bars P, S, with the end of the forwardly-
projecting frame.
_Fig. 53. Plan view._
The full page view, Fig. 53, represents a plan
view, with one of the wings cut away, showing the
general arrangement of the frame, and the three
wheels required for support, together with the
brace bars referred to.
The necessity of the rear end elevation will
now be referred to. The tail need not, necessarily,
be located at a point on a horizontal line
between the planes. It may be higher, or lower
than the planes, but it should not be in a position
to touch the ground when the machine is about
to ascend.
_Fig. 54. Alighting._
The angle of ascension in the planes need not
exceed 25 degrees so the frame does not require
an angle of more than 17 degrees. This is shown
in Fig. 54, where the machine is in a position
ready to take the air at that angle, leaving ample
room for the steering rudder.
ACTION IN ALIGHTING.--Also, in alighting, the
machine is banked, practically in the same
position thus shown, so that it alights on the rear
wheels O.
The motor U is usually mounted so its shaft is
midway between the planes, the propeller V being
connected directly with the shaft, and being behind
the planes, is on a medial line with the
machine.
The control planes L, M, N, are all connected up
by means of flexible wires with the aviator at the
set W, the attachments being of such a character
that their arrangement will readily suggest themselves
to the novice.
THE MONOPLANE.--From a spectacular standpoint
a monoplane is the ideal flying machine. It
is graceful in outline, and from the fact that it
closely approaches the form of the natural flyer,
seems to be best adapted as a type, compared with
the biplane.
THE COMMON FLY.--So many birds have been
cited in support of the various flying theories that
the house fly, as an example has been disregarded.
We are prone to overlook the small insect, but it
is, nevertheless, a sample which is just as potent
to show the efficiency of wing surface as the condor
or the vulture.
The fly has greater mobility than any other flying
creature. By the combined action of its legs
and wings it can spring eighteen inches in the
tenth of a second; and when in flight can change
its course instantaneously.
If a sparrow had the same dexterity, proportionally,
it could make a flight of 800 feet in the
same time. The posterior legs of the fly are the
same length as its body, which enable it to spring
from its perch with amazing facility.
_Fig. 55. Common Fly. Outstretched Wings._
The wing surface, proportioned to its body and
weight, is no less a matter for wonder and consideration.
In Fig. 55 is shown the outlines of the fly with
outstretched wings. Fig. 56 represents it with
the wing folded, and Fig. 57 is a view of a wing
with the relative size of the top of the body shown
in dotted lines.
_Fig. 56. Common Fly. Folded Wings._
The first thing that must attract attention, after
a careful study is the relative size of the body
and wing surface. Each wing is slightly smaller
than the upper surface of the body, and the thickness
of the body is equal to each wing spread.
_Fig. 57. Relative size of wing and body._
The weight, compared with sustaining surface,
if expressed in understandable terms, would be
equal to sixty pounds for every square foot of surface.
STREAM LINES.--The next observation is, that
what are called stream lines do not exist in the fly.
Its head is as large in cross section as its body,
with the slightest suggestion only, of a pointed
end. Its wings are perfectly flat, forming a true
plane, not dished, or provided with a cambre, even,
that upward curve, or bulge on the top of the aeroplane
surface, which seems to possess such a fascination
for many bird flight advocates.
It will also be observed that the wing connection
with the body is forward of the line A, which
represents the point at which the body will balance
itself, and this line passes through the wings
so that there is an equal amount of supporting
surface fore and aft of the line.
Again, the wing attachment is at the upper side
of the body, and the vertical dimension of the
body, or its thickness, is equal to four-fifths of the
length of he wing.
The wing socket permits a motion similar to a
universal joint, Fig. 55 showing how the inner
end of the wing has a downward bend where it
joins the back, as at B.
THE MONOPLANE FORM.--For the purpose of
making comparisons the illustrations of the monoplane
show a machine of 300 square feet of surface,
which necessitates a wing spread of forty
feet from tip to tip, so that the general dimensions
of each should be 18 1/2 feet by 8 1/2 feet at its
widest point.
First draw a square forty feet each way, as in
Fig. 58, and through this make a horizontal line
1, and four intermediate vertical lines are then
drawn, as 2, 3, 4, 5, thus providing five divisions,
each eight feet wide. In the first division the
planes A, B, are placed, and the tail, or elevator
C, is one-half the width of the last division.
_Fig. 58. Plan of Monoplane._
The frame is 3 1/2 feet wide at its forward end,
and tapers down to a point at its rear end, where
the vertical control plane D is hinged, and the
cross struts E, E, are placed at the division lines
3, 4, 5.
The angles of the planes, with relation to the
frame, are usually greater than in the biplane,
for the reason that the long tail plane requires
a greater angle to be given to the planes when
arising; or, instead of this, the planes A, B, are
mounted high enough to permit of sufficient angle
for initiating flight without injuring the tail D.
Some monoplanes are built so they have a support
on wheels placed fore and aft. In others
the tail is supported by curved skids, as shown
at A, Fig. 59, in which case the forward
supporting wheels are located directly beneath the planes.
As the planes are at about eighteen degrees
angle, relative to the frame, and the tail plane
B is at a slight negative angle of incidence, as
shown at the time when the engine is started, the
air rushing back from the propeller, elevates the
tail, and as the machine moves forwardly over
the ground, the tail raises still higher, so as to
give a less angle of incidence to the planes while
skimming along the surface of the ground.
_Fig. 59. Side Elevation, Monoplane._
In order to mount, the tail is suddenly turned
to assume a sharp negative angle, thus swinging
the tail downwardly, and this increases the angle
of planes to such an extent that the machine leaves
the ground, after which the tail is brought to the
proper angle to assure horizontal flight.
The drawing shows a skid at the forward end,
attached to the frame which carries the wheels.
The wheels are mounted beneath springs so that
when the machine alights the springs yield sufficiently
to permit the skids to strike the ground,
and they, therefore, act as brakes, to prevent the
machine from traveling too far.